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2014SprShotcreteEMag

Shotcrete Corner Shotcrete Testing around the World By Lars Balck CTesting—Who, Why, When, and How”1 in bility that is actually four separate tests: water-but is seldom measured in the United States. Inaddition, the QCS 2010 requires a test for duraShotcreteharles Hanskat’s article on “Shotcretethe Summer 2011 issue of magazine provided us with an excellent overview penetration, water absorption, rapid chloride of shotcrete testing in the United States. As penetration, and absorption. Charles pointed out, the purpose of testing is Testing around the world is really no different project quality assurance (QA), which should than testing in the United States. Project needs verify the designer’s intent, and quality control and often governing codes are what determine (QC), which should confirm the contractor’s which tests are needed or required on a project, performance. This article is meant to give the reader whether the project is in Atlanta, GA, or an introduction into the world of testing of concrete Shanghai, China. Engineers design structures to used for shotcrete outside the United States. carry design loads and endure environmental Fifty years ago, concrete was just tested for conditions. So project requirements dictate what compressive strength. No thought was given to tests are required. Mining and tunneling shotcrete durability other than the concept that “the stronger projects, whether in Canada or Latin America, the concrete, the longer it will last,” and to a are concerned about rapid strength gain, so early- degree, compressive strength of concrete is a good strength tests are conducted, and because most rough indicator of durability. Today, however, we tunnel and mining shotcrete is fiber reinforced, have a better understanding of concrete properties it is appropriate that tests for flexural toughness affecting durability. To properly evaluate concrete’s are typically specified. longevity, specific durability tests are needed to What makes testing around the world different give us a better indication of a concrete structure’s is standards and which standard developing orga- longevity for a particular service or environment nization (SDO) develops those standards. There than just testing for compressive strength alone. are many different standards throughout the world Durability requirements not only give us a to test for basically the same thing. Also, the test better understanding of the service life of a structure results can vary significantly depending on what but can vary depending on location. In Canada, standards are specified. For example, testing durability requirements are different than in the results for water-soluble chloride using the ASTM Middle East. Due to an extended exposure to standards can vary substantially from results using freezing conditions, concrete durability in Canada British standards due to far different procedures focuses on tests that measure concrete’s ability to used in the testing, even though both are supposed resist freezing-and-thawing cycles and resistance to result in determining the percentage of chloride to deicer salt scaling. In the Middle East, older in a material. concrete structures are crumbling from within due Every country wants to control commerce to corroding internal reinforcement. The corrosion within its borders, so every country specifies its is caused by salts and sulfates included in the own standards. Fortunately, most countries original concrete mixtures. Local cement, aggre- adopt common national standards developed by gates, and even water contain chlorides. To prevent independent SDOs that are developed using a internal corrosion, the Qatar Construction consensus process involving owners, suppliers, Standard (QCS) 2010 specifies frequent testing engineers, and contractors. The most prominent for chlorides per ASTM C1218, “Standard Test international standards are: Method for Water-Soluble Chloride in Mortar and • American Society Testing Materials (ASTM); Concrete.” This is the same test that ACI 318 • British Standards Institute (BSI); specifies for measuring chlorides in concrete, • Deutsches Institut fur Normung (DIN); 22 Shotcrete • Spring 2014


2014SprShotcreteEMag
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